docs: def save_pickle(obj, outfile, protocol=2):
      """Save the object as a pickle file
  
      Args:
          outfile (str): Filename
          protocol (int): Pickle protocol to use. Default is 2 to remain compatible with Python 2
  
      Returns:
          str: Path to pickle file
  
      """
      with open(outfile, 'wb') as f:
          pickle.dump(obj, f, protocol=protocol)
  
      return outfile